Well perforating apparatus



Oct. 15, 1968 J. B. SHQRE ET AL 3,405,769

WELL PERFORATING APPARATUS Filed Feb. 28, 1967 J5me: .5. JfioreINVENTURJ ATTORNE Y United States Patent 3,405,769 WELL PERFORATINGAPPARATUS James B. Shore, Friendswood, and William T. Bell,

Houston, Tex., assignors to Schlumberger Technology Corporation,Houston, Tex., a corporation of Texas Filed Feb. 28, 1967, Ser. No.619,393 6 Claims. (Cl. 175-453) ABSTRACT OF THE DISCLOSURE A perforatinggun is provided for through the flow line operations wherein bends inthe flow line require tools that are flexible in all planes. Theperforating gun includes a wire shaped charge carrier which has a lowcross sectional moment of inertia in the planes of its major and minoraxis to provide such flexibility. The shaped charges are made of wearresistant material and are arranged within the carrier to prevent theirinadvertent 1085 within the flow line.

Background of the invention This invention relates to 'a Wellperforating apparatus and, more particularly, to a perforating apparatushaving a flexible wire carrier for shaped charge explosive devices.

An important step in completing an oil well having a casing cemented inplace is to create perforations through the casing and cement around it,which perforations extend into the surrounding earth formations. Onewidely used method for perforating a well is to lower a plurality ofshaped explosive charge devices to levels in the well where oil bearingstrata have been found. The shaped charges, which are supported atpredetermined longitudinal spacings on a suitable carrier and areoriented in predetermined angular positions, are then detonated toproduce the perforations which extend through the metal well casing andthe surrounding cement into the oil bearing formation.

An important part of a shaped charge well perforating apparatus is thecarrier. The carrier must be strong enough and rigid enough to supportthe charge devices and maintain them in their proper alignment. Itshould be constructed so as to be readily assembled and shouldpreferably employ standardized, interchangeable parts which can beassembled in various configurations depending upon the number andspacing of the charge devices. A carrier meeting these characteristicsis set forth in a US. patent to W. T. Bell et al. No. 3,282,213.

Recent developments in underwater oil well completions require that welltools for use therein be more flexible than tools normaly used withconventional completions. These developments concern the completion ofoff shore wells by placing the well head assembly on the ocean floor. Asystem has been developed which utilizes a central gathering stationhaving several wells spaced therefrom and flow lines connecting thecentral gathering station with the well head assembly located on thefloor of a body of water. These flow lines, which may be of considerablelength, run horizontally along the ocean floor to the well head assemblyat which point a radius is formed in the flow line to permit the passageof flexible tools through the flow line around the radius and into thewell tubing string. Therefore, instead of using conventional floatingrigs for servicing such wells, a method is performed whereby wellservice tools are pumped through the flow line from the centralgathering platform. This movement of tools through the flow line isaccomplished by applying fluid pressure behind the tools to pump theminto position in the well. Well tools 3,405,769 Patented Oct. 15, 1968utilized in such a system must be of such flexibility as to be capableof being pumped through the flow line around the radius in the flow lineand into the tubing string. It is also readily seen that the loss of aportion of a tool within a flow line might cause jamming of the toolstherein. Sticking of tools within a flow line is critical since pumpingis the only means of recovery.

It is, therefore, an object of the present invention to provide a newand improved flexible perforating apparatus for pumping through the flowline of a Well.

Summary 0 the invention The present invention contemplates a perforatingapparatus comprising a pair of elongated wire members each havingalternate portions offset from and parallel to the longitudinal axis ofthe Wire members. When assembled as a carrier, the members are broughttogether along a central axis with the longitudinal axis of the membersand the central axis of the assembly lying in a longitudinally extendingplane. When assembled, the wire members have parallel spaced apart fiatportions adapted to receive encapsulated shaped explosive chargedevices. The flat portions of the wire members are adapted for receptionwithin circumferential grooves on the shaped charges. Alternate portionsof the wire members, between the shaped charges, are placed together ina sliding relationship. Means are provided for maintaining the alternateportions of the wire members relative to one another in such a slidingrelationship, such means preferably being a sleeve arranged about bothof the wire members when the wire members are assembled.

The novel features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of operation together with other objects andadvantages thereof, may best be understood by way of illustration andexample of certain embodiments when taken in conjunction with theaccompanying drawings.

Brief description of the drawings FIGURE 1 shows a well head assemblyand flow line with a string of perforating tools positioned in the flowline;

FIGURE 2 is a perspective view of a portion of the carrier which showsthe wire members arranged for holding the shaped charges;

FIGURE 3 is a partial end view of a shaped charge and one of the wiremembers; and

FIGURE 4 is a plan view of a shaped charge positioned within thecarrier.

Description of the preferred embodiments Referring first to FIGURE 1, astring of tools is shown positioned in a Well bore 12 for perforating awell by use of through the flow line techniques. A pair of parallel flowlines 13, 14 are shown entering a well head 16 and extending downwardlyinto the well bore. A packer device 17 isolates a portion of the wellbore. A landing seat 18 is provided in the lower end of the flow line 14to arrest downward travel of the well tools therein. Such through theflow line apparatus and techniques are described in greater detail incopending application Ser. No. 389,389.

The string of tools shown in FIGURE 1 includes a transport head 19having seal means thereon to provide a seal between the interior of theflow line and the tool to facilitate pumping of the tool string throughthe flow line. A connecting link 20 connects the transport head withhousing section 23 which carries a power source or batteries. A seatingshoulder 24 is formed on the housing 23 and provides a means forlocating the tool in the lower end of the flow tube, the seatingshoulder being engageable with the inwardly extending landing seat 18 atthe lower end of the flow tube to impede further travel of the toolstring therethrough. Housing 23 is connected by means of anotherconnecting link 24 to a switch section 26. The switch section has fiowtube engaging arms 27 for following the interior wall of the flow tube.At a selected position relative to the end of the flow tube, the armsare eifective upon their extension a preselected amount to close anelectrical circuit (not shown) within the string of tools. More than oneswitch section can be included in the string of tools with a typicalarrangement being shown in a copending patent application by James B.Shore filed Jan. 13, 1967.

A section of flexible tubing 28 is provided between the switch section26 and an eccentralizer housing 29 with the length of the flexibletubing being suflicient to provide proper positioning of the perforatingapparatus relative to the landing seat 18 in the fiow line. Theeccentralizer section 29 has a wall-engaging member 31 extendingtherefrom to push outwardly against the wall of the casing. Theeccentralizer maintains the perforating gun eccentered in the casing toprovide an optimum clearance between the shaped charges and the casingwall. A perforating gun 32 is connected to the lower end of theeccentralizer section 29 by any convenient means such as screws or thelike. The perforating gun includes a wire carrier 41 with shaped charges40 positioned therein and a detonating cord 42 connecting the chargeswith an electrical circuit (not shown) in the string of tools. Ablasting cap 43 is crimped or otherwise connected to the detonating cordand the electrical firing circuit to provide a detonating means. Stringsor wires 44 are used to secure the detonating cord relative to thecarrier 41.

FIGURE 2 shows the shaped charge carrier 41 in greater detail. Thecarrier is comprised of a pair of rectangularly shaped wire members 46,with each member having a plurality of alternating flat segments 47, 48parallel to the longitudinal axis of the member. Alternate ones of thesegments are offset to opposite sides of the longitudinal axis of themember and are connected at their ends by angular connecting segments49. To form the wire carrier, a pair of the wire members are arranged ina mirror image relationship with alternate flat segments 48 being placedtogether to leave the other alternate fiat segments 47 spaced apart. Thespaced apart segments form openings 51 into which shaped charge capsules40 are cooperatively received.

As shown in FIGURE 2, the wire members 46 are held against the oppositesides of the shaped charge capsule 40 by metal sleeves 52 which areslidably received about the Wire members along contacting segments 48.The sleeve 52 is sized to maintain the wire segments 48 in contactingrelationship with one another. However, at the same time, the sleeve 52fits loosely enough to permit relative sliding between the wire members46 when bending forces are applied to the wire members. Such relativesliding prevents the bending forces from producing a permanent set inthe wire members. The closeness of the adjacent segments 48 is importantin that the smaller the cross sectional area presented by the matingsegments 98, the less the cross sectional moment of inertia, therebyproviding greater flexibility of the carrier in the plane of greatestcross sectional dimension of the wire members. As shown in FIGURE 3, theplane of greatest cross sectional dimension or major axis of the wiremembers is normal to the side of the shaped charge and also normal tothe longitudinal axis of the wire members.

It has been found that the wire members must be made of a metal which,when subjected to the severe dynamic shock of the exploding shapedcharge devices, has sufiicient strength and tenacity to withstand suchdynamic shocks as well as possessing a low rate of crack propagation.Therefore, a strong material which is also relatively j 4 ductile andmalleable is suitable. Such a material is produced by heat treating 1065steel to provide a Rockwell hardness of around 40. It is readily seenthat the relative strength of the material to be used is dictated by themagnitude of explosive power produced by the shaped charge. Therefore,in certain situations, a lighter weight metal such as aluminum may beappropriate.

Accordingly, because the wire members are made of a relatively strongductile and malleable material and because of their geometric shape andcross section, the wire members of the present invention are capable ofsustaining the detonation of the charges they carry without fracture,and the carrier can be recovered in tact from the well after use. As aresult of charge detonation, a significant amount of erosion or pittingas well as compression occurs in the portion of the members where theshaped charge devices are supported. However, in as much as the materialis relatively ductile and has a correspondingly high toughness, theexplosive energy impinging upon the members is absorbed withoutproducing fracture and subsequent bending is possible without causingbreakage despite the erosion and pitting.

As shown in FIGURE 3, the case of the shaped charge device 40 hasoppositely disposed, outwardly extending, circumferential bosses 54, 56and a circumferential flange 58. Only one side of the charge device isshown in FIG- URE 3, but it will be understood that the opposite side isshaped in the same manner. The bosses define a first circumferentialgroove 60 for receiving one side of the wire member segment 47. A secondcircumferential groove 62, which is defined between the boss 56 and theflange 58, may alternatively receive the segment 47 of the wire member.Thus, the shaped charge devices can bemounted on the carrier ineither oftwo positions, and the distance at which the shaped charge devices aremounted from the wall of the well can be varied accordingly. Thepreferred type of shaped charge devices are those having frangible caseswhich disintegrate upon detonation of the explosive charges therein.Thus, no large pieces of the cases are left to block the well. Inaddition, because of the close dimensions of the flow tube through whichthe perforating device must be pumped, the shaped charge devices must bedesigned to withstand the wear imposed by such treatment. Therefore, acartridge made of a ceramic material which has such wear propertieswould suitably be used in such an application.

As shown in FIGURES 1 and 2, a plurality of shaped charge devices aremounted between the wire members in the manner shown in FIGURE 2 and arecoupled to the detonating cord 42. The cord, leading from the detonator,is positioned behind the carrier and held in place by a notched boss 64at the rear of each of the shaped charge devices which, in theembodiment illustrated in the drawings, are installed to point in thesame direction. Alternatively, of course, the shaped charges may beoriented in alternatively opposite directions with the cord 42 passingfrom one side of the plane of the wire members to the other.

To assemble the perforating device, the shaped charge device is placedbetween the wire members, the Wire members are positioned in the groovesof the shaped charges and a suitable hand tool is used to bend thesleeves around the abutting segments 48 of the wire members. Thedetonating cord 42 is then inserted into the notched bosses 64 on thecharge devices and tied to the carrier by means of wire or string 44. Itis noted, particularly in viewing FIGURE 4, that the angular connectingsegments 49 are spaced from one another a sufiicient distance to providea longitudinally enlarged opening 51 for receiving the shaped charges.The enlarged opening provides sufiicient clearance at each end of theopening to permit movement between the wire members and the shapedcharges. In addition, the circumferential grooves encircling the shapedcharges permit the shaped charges 40 to rotate as the Wire members moverelative to one another and relative to the shaped charges. Thus, thegroove insures that the shaped charge will remain captured by the wiremembers in the event of such rotative movement to prevent theirinadvertent loss in the flow line. In addition, the elongated opening 51which provides for such relative movement between the parts of theassembly, also prevents forces from being applied to the shaped chargeswhich might result from bending stresses on the wire members.

In the operation of this apparatus, when the perforating apparatus hasbeen assembled and placed in the flow tube for pumping into the well,pressure is applied to the flow tube behind the string of tools to pumpthe tool string through the flow line into the well bore. By necessity,loops are provided in the flow lines to facilitate entry of the flowline into the well head. Such loops generate small radiuses in a flowline around which the string of tools must be moved. The construction ofthe shaped charge carrier and shaped charges described herein permitsflexibility in more than one plane to thereby facilitate such movementthrough a flow line. Upon reaching a predetermined position in the well,the shaped charges are fired. Thereafter, pressure is applied to thebottom side of the transport head 19 via fiow line 13 and the string oftools is returned to the surface.

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects and,therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. In a carrier apparatus for holding explosive charges for perforatinga well, a pair of wire members each having alternate first and secondstraight portions parallel to the longitudinal axis of each of saidmembers, said first and second straight portions being offset from oneanother one opposite sides of said longitudinal axis of said member,said members being arranged so that alternate first straight portionsare arranged parallel to one another and slidably held together to forma section having a minimum cross sectional moment of inertia andalternate second straight portions are arranged parallel to one anotherand spaced apart to form a space for cooperatively accommodating ashaped charge device.

2. The apparatus of claim 1 wherein said wire members have fiat opposingsurfaces.

3. The apparatus of claim 1 wherein said wire members have a rectangularcross section.

4. The apparatus of claim 1 and further including a sleeve slidablyreceived about said first straight portions.

5. A perforating gun for use in a well bore including: a wire carrierhaving a pair of wire members arranged to provide flexibility in theplanes of its major and minor axis; and means for holding said wiremembers together at portions along their length and at the same timepermitting relative sliding movement between said wire members; saidwire members having spaced apart portions providing an opening, whenassembled, for receiving a shaped charge; said spaced apart portionshaving opposed straight surfaces for contacting and holding the shapedcharge within the opening.

6. The apparatus of claim 5 and further including a shaped chargepositioned within said opening, said shaped charge having acircumferential groove encircling said shaped charge for receiving theopposed straight surfaces of said wire members.

References Cited UNITED STATES PATENTS 2,799,224 7/1957 Long -4.6 X2,981,185 4/1961 Caldwell 1754.6 X 3,036,521 5/1962 Owen 1754.63,100,443 8/1963 Pohoriles 175-4.6 X 3,282,213 11/1966 Bell et al.175-46 X DAVID H. BROWN, Primary Examiner.

